Material handling vehicle with dual control handle system

ABSTRACT

A material handling vehicle includes an operator compartment having two operator control handles, a deadman switch accessible by an operator using either control handle, and a traction system. The traction system is controlled by the control handles to drive the vehicle in a selected direction, wherein an operator can control the traction system while facing one of the selected directions and the deadman switch is selectively activatable to enable operation from both control handles.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/240,301, filed Sep. 29, 2008, now U.S. Pat. No. 7,658,259 which is acontinuation of U.S. patent application Ser. No. 10/631,239, filed Jul.31, 2003, now U.S. Pat. No. 7,428,943 both of which are fullyincorporated herein by reference.

STATEMENT CONCERNING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

The present invention relates to material handling vehicles, and moreparticularly to a material handling vehicle with ergonomic multiplecontrol handles for operation in a variety of operator orientations.

Material handling vehicles commonly found in warehouse and factoryenvironments include, for example, vehicles in which the operatornormally stands on a platform at the rear of the truck, at the endopposite of a load carrying or load handling mechanism, typicallyemploying forks to lift and transport material. To provide an efficientflow of goods in such facilities, operators of these vehicles typicallyorient their bodies in the most comfortable position for adequatevisibility to drive the material handling vehicles in both a forks firstdirection, with the vehicle forks leading in the direction of travel,and tractor first direction, in which the vehicle forks trail in thedirection of travel.

Although in a typical vehicle there are a variety of possible operatororientations, when traveling, an operator will favor positions thatmaximize comfort and visibility for forks first and tractor firsttravel. Generally, one operator orientation is used more frequently thanthe others. The prevalent orientation varies with vehicle design, fromfacility to facility, within a given facility, and even from operator tooperator. There is, therefore, a fundamental need to provide stabilityto the operator when traveling for all likely orientations, whilemaintaining operator comfort and the maximum productivity potential ofthe vehicle.

For these reasons, designers of lift trucks have developed a number ofdifferent operator compartment configurations. Available configurationsinclude both standing and seated configurations in which the operatorfaces either generally to one side or to the front/rear of the truck.Vehicles designed for a standing operator (stand-up vehicles), includeboth side stance configurations where the operator generally operatesthe truck when standing facing the left side of the truck and, fore/aftconfigurations in which the operator may either stand facing the load oraway from the load. For each of these configurations, designers havefurther provided various methods to accommodate operator stability fortravel in both the forks first and tractor first directions, and toprovide each design with a reasonable degree of comfort for theoperator, while ensuring the capability for vehicle productivity.Stand-up vehicle designs, for example, typically impart stability, inpart, through hand operated vehicle controls that provide both stabilityand the means to control the operation of the vehicle. Operatorstability when traveling is accomplished through a combination of asolid footing, pads and covers that embrace portions of the operatorsbody, hands on the vehicle controls and an operator advanced knowledgeof the commanded vehicle motions.

Typical prior art stand-up vehicles utilize the same control elements tocommand travel in either direction and for either stance orientation.That is, the truck operator manipulates the same steering device, travelcontrol, and deadman foot control regardless of stance orientation. Inthe case of stand-up trucks configured in the fore/aft sense, althoughdesigned to be intuitive for bi-directional control, some operatorsnonetheless find the controls more convenient for forks first travelthan for tractor first travel. Furthermore, these controls often do notprovide maximum comfort for the widest possible range of operator sizes,as the operator must reach beside and slightly rearward of his or hercenterline in order to control the vehicle travel speed when driving andfacing in the tractor first direction.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a material handlingvehicle including an operator compartment having two operator controlhandles, a deadman switch accessible by an operator using either controlhandle, and a traction system. The traction system is controlled by thecontrol handles to drive the lift truck in a selected direction, whereinan operator can control the traction system while facing the selecteddirection and the deadman switch is selectively activatable to enableoperation from both control handles.

In another aspect of the invention, an operator compartment for amaterial handling vehicle is provided. The operator compartment includestwo control handles, a first control handle mounted for access by anoperator facing a first direction, and an second control handle mountedfor access by an operator facing a second direction. A deadman switchand a steering wheel are each positioned in the compartment to beaccessible by an operator using either control handle.

These and other objects, advantages and aspects of the invention willbecome apparent from the following description. In the description,reference is made to the accompanying drawings which form a part hereof,and in which there is shown a preferred embodiment of the invention.Such embodiment does not necessarily represent the full scope of theinvention and reference is made therefore, to the claims herein forinterpreting the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a material handling vehicle constructed inaccordance with the present invention with the operator facing aft.

FIG. 2 is a block diagram of the lift truck constructed in accordancewith the present invention.

FIG. 3 is a perspective view of a multi-function control handle of FIGS.1 and 2.

FIG. 4 is a perspective view of an aft control handle of FIGS. 1 and 2.

FIG. 5 is a top view of the material handling vehicle with the operatorfacing fore.

FIG. 6 is a cutaway side view of the material handling vehicle of FIG.1, showing an operator using the aft control handle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the Figures, and more particularly to FIG. 1, amaterial handling vehicle constructed in accordance with the presentinvention is shown. The material handling vehicle as shown is astand-up, fore-aft stance configured lift truck 10 designed to allow theoperator to stand facing in the direction of travel, whether travel bein the Forks First or Tractor First direction. The truck 10 includes anoperator compartment 11 comprising an enclosure 17 with an opening 19for entry and exit of the operator.

The compartment 11 includes a first multi-function control handle 14which is mounted to the enclosure 17 at the front of the operatorcompartment 11 proximate the forks 31, an aft control handle 13positioned at the back of the compartment 11, and a floor switch 20positioned on the floor 21 of the compartment 11 in a location selectedto allow the operator to easily access the floor switch 20 when facingeither the fore or aft direction. A steering wheel 16 is also providedin the compartment 11 and, like the floor switch, is positioned to allowcontrol by the operator when facing either the fore or aft directions.The position of multi-function control handle 14 is selected to controlthe speed and direction of travel of the lift truck 10 when the operatoris facing the forks 31, and the aft control handle 13 is positioned tocontrol the motion of the lift truck 10 when the operator is facing inthe aft-facing direction, as described more fully below.

Referring now to FIG. 2, a block diagram of a typical lift truck 10 inwhich the present invention can be provided is illustrated. The lifttruck 10 comprises a vehicle control system 12 which receives operatorinput signals from the aft control handle 13, the multi-function controlhandle 14, the steering wheel 16, a key switch 18, and the floor switch20 and, based on the received signals, provides command signals to eachof a lift motor control 23 and a drive system 25 including both atraction motor control 27 and a steer motor control 29. The drive system25 provides a motive force for driving and steering the lift truck 10 ina selected direction, while the lift motor control 23 drives forks 31along a mast 33 to raise or lower a load 35, as described below. Thelift truck 10 and vehicle control system 12 are powered by one or morebattery 37, coupled to the vehicle control system 12, drive system 25and lift motor control 23 through a bank of fuses or circuit breakers39.

As noted above the operator inputs include a key switch 18, floor switch20, steering wheel 16, a multi-function control handle 14, and an aftcontrol handle 13. The key switch 18 is activated to apply power to thevehicle control system 12, thereby enabling the lift truck 10. The floorswitch 20 provides a deadman braking device, disabling motion of thevehicle unless the floor switch 20 is activated by the operator, asdescribed below.

Referring now also to FIGS. 1 and 3, the control handle 14 is amulti-function control which includes both an upright, substantiallyvertical section 24, and a horizontal section 26, the vertical 24 andhorizontal 26 sections together providing a number of control functionsfor the lift truck 10. The horizontal section 26 includes a transducersuch as a potentiometer which provides a travel direction and speedcommand signal to the lift truck 10 and is configured to provideintuitive control for an operator facing the fore of the lift truck 10or the forks first direction. The horizontal section 26 is rotatedforward towards the forks 31 of the lift truck 10 to provide a forksfirst directional and speed command and backwards away from the forks 31to provide a tractor first directional and speed signal to the vehiclecontrol 12, the final speed of travel being determined in both casesbased on the degree of rotation. The vertical section 24 includes afour-way switch 15 located on the top of the control handle 14 whichprovides a tilt up/down function when activated in the forward andreverse directions and a sideshift right and left function whenactivated to the right and left directions. A plurality of controlactuators 41 located on the vertical section of the control handle 14provide a number of additional functions, and can include, for example,a reach push button, a retract push button, and a horn push button. Thevertical sectional portion further includes a transducer such as apotentiometer providing a lift function control signal to the vehiclecontrol system 12. A number of other functions could also be provided,depending on the construction and intended use of the lift truck 10.

Referring now to FIGS. 1, 2, and 4, the aft control handle 13 is ahorizontally mounted handle which provides directional and speed controlsignals to the vehicle control system 12 as described with reference tothe horizontal section of the control handle 14 described above. The aftcontrol handle 13 is configured to operate intuitively, and similarly tothe control handle 14, for an operator facing the aft of the vehicle.The aft control handle 13 is rotated forward toward the aft of the lifttruck 10 to provide a tractor first directional signal and speedcommand, and in the opposite direction, toward the fore of the lifttruck 10, to provide a forks first directional signal and speed command.Therefore, irrespective of the direction that the operator is facing, acontrol handle with intuitive operation is provided. When facing eitherdirection, a control is provided which is rotatable in the directionthat the operator is facing to cause the lift truck 10 to move in thatdirection, and which is also rotatable in the opposite direction tocause the lift truck 10 to move in the opposite direction. As describedabove, the speed request signal provided by the aft control handle 13 isa function of the amount of rotation in a given direction.

Referring again to FIG. 2, as shown, the vehicle control system 12receives a control signal from at least one of the control handle 14 andaft control handle 13 and transmits the control signal to traction motorcontrol 27. Traction motor control 27 activates the traction motor 43which is connected to wheel 45 to provide motive force to the lift truck10. The speed and direction of the traction motor 43 and associatedwheel is selected by the operator from the control handles 13 and 14,and is typically monitored and controlled through an encoder or otherfeedback device (not shown) coupled to the traction motor 43. As shown,each of the control handles 13 and 14 provide an individual controlsignal to the vehicle control system 12 and traction control system 27.In this case, the vehicle control system 12 evaluates the signalsprovided by each of the control handles 13 and 14 and determines anappropriate speed and direction of travel. Alternatively, the controlhandles 13 and 14 could be mechanically linked, with either one of thecontrol handles providing a control signal to the vehicle control system12. In other embodiments, the control handles 13 and 14 can beselectively activated using mechanical or electrical switch devices,activated or deactivated through user interfaces such as the display 55described below, or otherwise regulated.

The wheel 45 is also connected to friction brake 22 through the drivemotor, providing both a service and parking brake function for the lifttruck 10. The friction brake 22 is typically spring applied, anddefaults to a “brake on” position. The operator must stand on thedeadman pedal, actuating floor switch 20, for the brake to be released.The traction motor 43 is typically an electric motor, and the associatedfriction brakes 22 can be either an electrically or a hydraulicallyreleased devices. Although one friction brake 22, motor 43, and wheel 45are shown, the lift truck 10 can include one or more of these elements.

The steer motor control 29 is connected to drive a steer motor 47 andassociated steerable wheel 49, steered in a direction selected by theoperator by rotating the steering wheel 16, described above. Thedirection of rotation of the steerable wheel 49 determines the directionof motion of the lift truck.

The lift motor control 23 provides command signals to control a liftmotor 51 which is connected to a hydraulic circuit 53 for driving theforks 31 along the mast 33, thereby moving the load 35 up or down,depending on the direction selected at the multi-function control handle14. In some applications, the mast 33 can be a telescoping mast. Here,additional hydraulic circuitry can be included to raise or lower themast 33 as well as the forks 31.

In addition to providing control signals to the drive system and liftcontrol system, the vehicle control 12 can also supply data to a display55 for providing information to the operator. Displayed information caninclude, for example, a weight of a load placed on the forks 31, thespeed of the vehicle, the time of day, or the state of charge of thebattery.

Referring now to FIGS. 1 and 4, as described above, the aft controlhandle 13 is horizontally mounted and is preferably provided as acylindrically-shaped, twist grip style handle. The twist grip handle isadvantageous because it is relatively small and provides a full range ofmotion in limited space and, further, provides stability to the operatoras the lift truck 10 is in motion. The center core of the aft controlhandle 13 can be mounted directly to a frame of the lift truck 10, andthe outer grip 28 responds to rotational forces about the center axis ofthe aft control handle 13, remaining stationary relative to armmovements and forces up, down, left, right, toward and away from theoperator. The aft control handle 13 is preferably mounted at a height ofabout thirty-eight inches above the floor 21, and angled front to back(FIG. 1) at an angle of about seventy degrees to the adjacent side wallof operator compartment 11. At this height and angle, the aft controlhandle 13 has been shown to fit comfortably in an operator's hand at aneutral hand position, and further to be substantially perpendicular tothe axis of the operator's arm in use, providing a comfortable grip foroperators varying in height between the bottom 5 percent of females andthe top 95 percent of males, therefore providing an ergonomic controlfor virtually all operators. Preferably, the outer grip 28 is a smoothmaterial molded to include recessed grooves 30, which provide apositive, comfortable grip. Although a number of suitable materials areavailable, one material useful in this application is 10% glass filledpolycarbonate thermoplastic. The smooth material grip 28 and recessedgrooves 30 are selected to provide a positive yet comfortable grip, andallow for easy movement of the grip around the handle. Referring stillto FIG. 4, control handle 13 also includes horn push button 48 allowingan aft-facing operator to sound a warning without removing his or herhand from the handle.

Referring now to FIG. 6, a side view of the lift truck 10 showing anoperator facing aft is shown. In this position, the operator grips theaft control handle 13, such that the operator is facing in the directionof motion. The shape and position of the aft control handle 13 allowindividuals of various heights to grip the aft control handle 13 from avariety of approach angles and grip positions. As described above,operation of the handle is simple and intuitive, allowing rotation inthe direction of travel when the operator is facing aft, as shown.

Referring now to FIGS. 1, 5, and 6, in operation, the operator stands inthe operator compartment 11 selectively facing either the fore, forksfirst direction (FIG. 5), or the aft, tractor first direction (FIGS. 1,6). When operating the lift truck in the forks first direction, theoperator controls the direction and speed of motion using themultifunction control handle 14, as described above. The deadman switch20 provided on the floor of the operator compartment 11 is positioned tobe activated or deactivated by the left foot, and the steering wheel 16is, likewise, operated by the left hand when the lift truck is operatedin the forks first mode.

Referring now to FIGS. 1 and 6, while facing the aft direction of thelift truck and particularly for operating the lift truck in the aft ortractor first direction, the operator controls the direction and speedof travel of the lift truck with his or her left hand using the aftcontrol handle 13, and operates the floor switch 20 and steering wheel16 with the right foot and hand respectively. While facing either thefore or aft directions, therefore, the operator can control the speedand direction of the lift truck 10 with an operator control handle whichis positioned to the side and ahead of the operator's centerline. Thisarrangement provides improved ease of control, and further providesstability for the operator, allowing the operator to grip a control inthe direction the operator is facing. Furthermore, as the operator isnot required to reach beside and slightly rearward of his or hercenterline when facing in the aft direction to control travel of thelift truck, the operation is more comfortable, which is not onlyadvantageous for the operator, but improves the overall productivitypotential of the lift truck by decreasing the need for operator breaksduring operation.

Although it is advantageous for the operator to control the travel oflift truck 10 with the multi-function control handle 14 when facing theforks and traveling in the forks first direction and the aft controlhandle 13 when facing the aft and traveling in the tractor firstdirection, either control handle 13 or 14 can be used to control thedirection and speed of the lift truck in either direction. Typically,however, an operator will elect to control the lift truck with the aftcontrol handle 13 when the lift truck 10 is operated for an extendedperiod of time traveling in the tractor first direction and with thecontrol handle 14 when operating for an extended period of travel in theforks first direction and when operating the load handling controlsincluded on multi-function control handle 14.

Although the invention has been described with respect to a stand-up,fore-aft configuration lift truck, it will be apparent that thetechniques disclosed can be applied to side-stance and seated-operatortrucks as well, and nothing disclosed herein should be construed tolimit the teaching of the invention to stand-up, fore-aft configurationtrucks. Furthermore, while the invention has been described withreference to a lift truck, the invention could be applied to variousother types of material handling vehicles.

While there has been shown and described what are at present consideredthe preferred embodiments of the invention, it will be obvious to thoseskilled in the art that various changes and modifications can be madetherein without departing from the scope of the invention defined by theappended claims.

1. A material handling vehicle, comprising: an operator compartment; afirst operator control handle for selecting a direction and a speed ofvehicle travel, the first control handle being mounted in the operatorcompartment and configured for operation in a first vehicle direction; asecond operator control handle for selecting a direction and a speed ofvehicle travel, the second operator control handle mounted in thecompartment and configured for operation in a second vehicle direction;a deadman switch in a position accessible by an operator operating thevehicle using at least one of the first control handle and the secondcontrol handle, the deadman switch being selectively activatable toenable operation from both the first operator control handle and thesecond operator control handle; and a traction system controlled by thefirst and second operator control handles to selectively drive thevehicle in the first vehicle direction and the second vehicle direction,wherein an operator can control the traction system while facing one ofthe first vehicle direction and the second vehicle direction.
 2. Thematerial handling vehicle as defined in claim 1, wherein the firstoperator control handle is a multi-function control handle.
 3. Thematerial handling vehicle as defined in claim 1, wherein the firstoperator control is mounted at a first end of the operator compartment.4. The material handling vehicle as defined in claim 3, wherein thesecond operator control handle is mounted to a second end of theoperator compartment.
 5. The material handling vehicle as defined inclaim 1, wherein the first operator control handle is movable about anaxis and said second operator control handle is movable about an axis.6. The material handling vehicle as defined in claim 5, in which axisabout which the first operator control handle is movable and the axisabout which the second operator control handle is movable are notcoaxial.
 7. The material handling vehicle as defined in claim 6, inwhich one of said operator control handles includes a vertical section.8. The material handling vehicle as defined in claim 1, furthercomprising a floor in the compartment, and the deadman switch is mountedto the floor.
 9. The material handling vehicle as defined in claim 1,wherein the second operator control is mounted at an angle as referencedto a side of the compartment selected to be substantially perpendicularof an arm of the operator when operating the second operator control.10. The material handling vehicle as defined in claim 1, including asteering wheel mounted to the compartment, the steering wheel beingpositioned on the compartment in a location to allow an operator torotate the steering wheel when using either the first control handle orthe second control handle.
 11. The material handling vehicle as definedin claim 1, wherein the second operator control handle includes a hornactuator for activating a horn.
 12. An operator compartment for amaterial handling vehicle comprising: a first control handle mounted foraccess by an operator facing a first direction, said first controlhandle being movable about an axis; a second control handle mounted foraccess by an operator facing a second direction, the second controlhandle being movable about an axis; a deadman switch accessible by anoperator using the first control handle when facing the first directionand the second control handle when facing the second direction; and asteering wheel accessible by an operator using the first control handlewhen facing the first direction and accessible by an operator using thesecond control handle when facing the second direction.
 13. The materialhandling vehicle of claim 12, wherein the first and second vehicledirections are fore and aft directions of the vehicle.
 14. The materialhandling vehicle of claim 12 wherein the second control handle issubstantially horizontal.
 15. The material handling vehicle as definedin claim 12, in which axis about which the first operator control handleis movable and the axis about which the second operator control handleis movable are not coaxial.
 16. The material handling vehicle as definedin claim 12, wherein the first and second control handles are eachmovable around a substantially horizontal axis.
 17. The materialhandling vehicle as defined in claim 12, wherein each of the first andsecond control handles are movable in the second and first directions,respectively, to provide a control signal indicative of motion in thedirection opposite the direction the operator is facing.
 18. Thematerial handling vehicle as defined in claim 12, wherein the secondcontrol handle is a twist grip handle.